The present invention relates to a facsimile system, and more particularly, to a method for transmitting pages of a document upon generation of an error during communication in a facsimile system.
In a conventional facsimile system, when a user dials a receiving subscriber's telephone number after inserting pages of a document to be transmitted into a document feeding cassette, the document pages are transmitted according to a predetermined protocol. When calling the receiving subscriber's facsimile system, the transmitting subscriber's facsimile system transmits a calling tone (hereinafter, "CNG") signal to the receiving subscriber's facsimile system. In response to the CNG signal, the receiving subscriber's facsimile system transmits a called station identification (hereinafter, "CED") signal, and subsequently transmits a non-standard facilities (hereinafter, "NSF") signal, a called subscriber identification (hereinafter, "CSI") signal and a digital identification (hereinafter, "DIS") signal. At this time, the transmitting subscriber's facsimile system analyzes the NSF signal to thereby determine whether or not an image quality change is requested. If an image quality change is requested, the transmitting subscriber's facsimile system changes the image quality mode according to the image quality change request, and transmits a non-standard set up (hereinafter, "NSS") signal, a transmitting subscriber identification (hereinafter, "TSI") signal and a digital command signal (hereinafter, "DCS") to the receiving subscriber's facsimile system. Next, the receiving subscriber's facsimile system transmits a confirmation to receive (hereinafter, "CFR") signal to the transmitting subscriber's facsimile system. The transmitting subscriber's facsimile system transmits image data from a document to the receiving subscriber's facsimile system in response to the CFR signal. After one page of image data is transmitted, the transmitting subscriber's facsimile system transmits an end of page (hereinafter, "EOP") signal to the receiving subscriber's facsimile system. In response to the EOP signal, the receiving subscriber's facsimile system transmits a message confirmation (hereinafter, "MCF") signal to the transmitting subscriber's facsimile system, thus completing the transmission and reception of one page of image data. Then, in order to receive a next page of image data, the receiving subscriber's facsimile system again transmits the NSF, CSI and DIS signals to the transmitting subscriber's facsimile system to thereby repeat the previously described operations. The protocol for transmitting and receiving document images in this manner is prescribed in the Consultive Committee in International Telephone and Telegraph (hereinafter, "CCITT") recommendation. This protocol, and a protocol in accordance with a CCITT.41420 standard is performed through five phases as shown in Table &lt;1&gt;.
TABLE 1 ______________________________________ TRANSMITTING SYSTEM RECEIVING SYSTEM ______________________________________ PHASE A CALLING(CNG) CALLED STATION IDENTIFICATION(CED) PHASE B COMMAND CAPABILITIES INFORMATION IDENTIFICATION (NSS + TSI + DCS) (NSF + CSI + DIS) TRAINING (HIGH SPEED) CONFORMATION TO (9600/7200/4800/2400) RECEIVE (CFR) PHASE C MESSAGE HIGH SPEED (9600/7200/4800/2400) PHASE D END OF MESSAGE CONFIRMATION TO (EOP/MPS/EOM/RPI.sub.-- Q) RECEIVE (MCF/RTP/RTN/PIP/PIN) PHASE E DISCONNECT THE LINE (DCN) ______________________________________
As shown in Table &lt;1&gt;, in phase A, which is a call set-up phase, the transmitting and receiving systems exchange the CNG and CED signals. In phase B, which is a pre-message procedure phase, the transmitting and receiving systems exchange the NSS+TSI+DCS and NSF+CSI+DIS and CFR signals. Phase C is a phase for transmitting a facsimile message (image data). Phase D is a post-message procedure phase. In phase D, the transmitting and receiving systems exchange the EOP/MPS/EOM/RPI.sub.-- Q and the MCF/RTP/RTN/PIP/PIN signals. In phase E, the transmitting system transmits a disconnection (hereinafter, "DCN") signal to the receiving system, and the call is released.
In the conventional facsimile system, however, if an error is generated or there is no response from a counterpart's facsimile system during transmission and reception of document data according to the previously described protocol, a message indicating that an error has occurred or that no response has occurred is displayed. If the error is generated during transmission of the document data, the error message is displayed and transmission is then terminated. At this time, if a user presses a re-dial key, the receiving subscriber's telephone number is re-dialed at a predetermined time interval, and communication is re-attempted as many times as is designated by the user.
In this conventional facsimile system, when an error is generated during communication, only the error message is displayed and transmission of the document data is terminated. Therefore, there is a disadvantage in that when an error is generated while transmitting several document pages, the user has to re-transmit all of the document pages, irrespective of whether some of the pages have been successfully transmitted, thereby wasting the user's time and incurring unnecessary telephone charges. The present invention is directed towards solving this problem.